From 694f1b0ec3c119d4625dd1ab10145aed23642a6b Mon Sep 17 00:00:00 2001 From: Hunter Kvalevog Date: Thu, 13 Nov 2025 18:14:17 -0600 Subject: gl-vfog --- gl-vfog/main.cc | 281 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 281 insertions(+) create mode 100644 gl-vfog/main.cc (limited to 'gl-vfog/main.cc') diff --git a/gl-vfog/main.cc b/gl-vfog/main.cc new file mode 100644 index 0000000..d14ff38 --- /dev/null +++ b/gl-vfog/main.cc @@ -0,0 +1,281 @@ +// OpenGL volumetric fog demo +// +// SPDX-License-Identifier: 0BSD +// +// Changelog: +// - 11/13/25: Initial release +// + +#define GLAD_GL_IMPLEMENTATION +#include "../common/c_cpp/thirdparty/glad33/glad33.h" + +#include +#include +#include + +#define IMGUI_IMPL_OPENGL_LOADER_CUSTOM +#include "imgui.h" +#include "imgui_impl_opengl3.cpp" +#include "imgui_impl_sdl3.cpp" + +#include "geometry.hh" + +// Helper: Report errors via glGetError() after every OpenGL function call. +// macOS does not support glDebugMessageCallback +static void assert_gl_error(GLenum error, const char* expr, int line) +{ + if (error != GL_NO_ERROR) { + const char* error_string; + switch (error) { +#define BIND_ERROR(name) case name: { error_string = #name; }; break; + BIND_ERROR(GL_INVALID_ENUM); + BIND_ERROR(GL_INVALID_VALUE); + BIND_ERROR(GL_INVALID_OPERATION); + BIND_ERROR(GL_INVALID_FRAMEBUFFER_OPERATION); + BIND_ERROR(GL_OUT_OF_MEMORY); +#undef BIND_ERROR + default: SDL_assert(0 && "Invalid GL_ERROR enum"); + } + SDL_Log("[Line #%u] %s caused %s\n", line, expr, error_string); + } +} +#define GL(expr) \ + expr; \ + for (GLenum _glcode; (_glcode = glGetError()) != GL_NO_ERROR; ) { \ + assert_gl_error(_glcode, #expr, __LINE__); \ + } + +int main(int argc, char* argv[]) +{ + (void)argc; + (void)argv; + + if (!SDL_Init(SDL_INIT_VIDEO | SDL_INIT_EVENTS)) { + fprintf(stderr, "Failed to initialize SDL: %s\n", SDL_GetError()); + return EXIT_FAILURE; + } + + SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3); + SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 3); + SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE); + SDL_GL_SetAttribute(SDL_GL_MULTISAMPLEBUFFERS, 1); + SDL_GL_SetAttribute(SDL_GL_MULTISAMPLESAMPLES, 4); + + SDL_Window* wnd = SDL_CreateWindow("gl-vfog", 1024, 768, SDL_WINDOW_OPENGL); + if (!wnd) { + fprintf(stderr, "Failed to create window: %s\n", SDL_GetError()); + return EXIT_FAILURE; + } + + if (!SDL_GL_CreateContext(wnd)) { + fprintf(stderr, "Failed to create OpenGL context: %s\n", SDL_GetError()); + return EXIT_FAILURE; + } + SDL_GL_SetSwapInterval(1); + + if (!gladLoadGL(SDL_GL_GetProcAddress)) { + fprintf(stderr, "Failed to load OpenGL functions\n"); + return EXIT_FAILURE; + } + + IMGUI_CHECKVERSION(); + ImGui::CreateContext(); + ImGui_ImplSDL3_Init(wnd, 0, 0); + ImGui_ImplOpenGL3_Init(); + ImGui::GetIO().IniFilename = NULL; + + // + // 0 1 + // +------------+ + // /| /| + // 4 / | 5 / | + // +------------+ | + // | | | | + // | | 3 | | 2 + // | +---------|--+ + // | / | / + // 7 |/ 6 |/ + // +------------+ + // + + const float vdata[] = { + 0.0f, 1.0f, 0.0f, + 1.0f, 1.0f, 0.0f, + 1.0f, 0.0f, 0.0f, + 0.0f, 0.0f, 0.0f, + 0.0f, 1.0f, 1.0f, + 1.0f, 1.0f, 1.0f, + 1.0f, 0.0f, 1.0f, + 0.0f, 0.0f, 1.0f, + }; + + const uint16_t idata[] = { + 1, 0, 3, + 1, 3, 2, + 5, 1, 2, + 5, 2, 6, + 4, 5, 6, + 4, 6, 7, + 0, 4, 7, + 0, 7, 3, + 0, 1, 5, + 0, 5, 4, + 7, 6, 2, + 7, 2, 3, + }; + + GLuint vao; + GL(glGenVertexArrays(1, &vao)) + GL(glBindVertexArray(vao)); + + GLuint vbo; + GL(glGenBuffers(1, &vbo)); + GL(glBindBuffer(GL_ARRAY_BUFFER, vbo)); + GL(glBufferData(GL_ARRAY_BUFFER, sizeof(vdata), vdata, GL_STATIC_DRAW)); + + GLuint ibo; + GL(glGenBuffers(1, &ibo)); + GL(glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ibo)); + GL(glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(idata), idata, GL_STATIC_DRAW)); + + GL(glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(float) * 3, NULL)); + GL(glEnableVertexAttribArray(0)); + + struct { + GLenum type; + const char* path; + } shaders[] = { + { .type = GL_VERTEX_SHADER, .path = "vs.glsl" }, + { .type = GL_FRAGMENT_SHADER, .path = "fs.glsl" }, + }; + + GLuint prog = GL(glCreateProgram()); + for (size_t i = 0; i < sizeof(shaders) / sizeof(*shaders); ++i) { + const char* src = (const char*)SDL_LoadFile(shaders[i].path, NULL); + if (!src) { + fprintf(stderr, "Failed to load shader %s: %s\n", shaders[i].path, SDL_GetError()); + return EXIT_FAILURE; + } + + GLuint shader = GL(glCreateShader(shaders[i].type)); + GL(glShaderSource(shader, 1, &src, NULL)); + GL(glCompileShader(shader)); + GLint compile_status = 0; + GL(glGetShaderiv(shader, GL_COMPILE_STATUS, &compile_status)); + if (compile_status != GL_TRUE) { + char error[1024] = { 0 }; + GL(glGetShaderInfoLog(shader, sizeof(error), NULL, error)); + SDL_Log("Error compiling shader %s: %s\n", shaders[i].path, error); + return EXIT_FAILURE; + } + GL(glAttachShader(prog, shader)); + } + GL(glLinkProgram(prog)); + + GLint prog_status; + GL(glGetProgramiv(prog, GL_LINK_STATUS, &prog_status)); + if (prog_status != GL_TRUE) { + char error[1024] = { 0 }; + GL(glGetProgramInfoLog(prog, sizeof(error), NULL, error)); + SDL_Log("Error linking program: %s\n", error); + return EXIT_FAILURE; + } + + GL(glUseProgram(prog)); + + GLuint u_view = GL(glGetUniformLocation(prog, "u_view")); + GLuint u_cam = GL(glGetUniformLocation(prog, "u_cam")); + GLuint u_time = GL(glGetUniformLocation(prog, "u_time")); + GLuint u_mode = GL(glGetUniformLocation(prog, "u_mode")); + GLuint u_sigma = GL(glGetUniformLocation(prog, "u_sigma")); + + bool running = true; + while (running) { + SDL_Event evt = { 0 }; + while (SDL_PollEvent(&evt)) { + ImGui_ImplSDL3_ProcessEvent(&evt); + switch (evt.type) { + case SDL_EVENT_QUIT: { + running = false; + } break; + } + } + + int wnd_x = 0; + int wnd_y = 0; + SDL_GetWindowSizeInPixels(wnd, &wnd_x, &wnd_y); + + ImGui_ImplSDL3_NewFrame(); + ImGui_ImplOpenGL3_NewFrame(); + ImGui::NewFrame(); + + // Controls + static int c_mode = 0; + static float c_sigma = 4.0f; + static float c_zoom = 1.5f; + ImGui::SetNextWindowPos(ImVec2(15, 15)); + ImGui::SetNextWindowSize(ImVec2(150, 768 - 30)); + if (ImGui::Begin("Controls", NULL, ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoResize)) { + ImGui::SeparatorText("Controls"); + ImGui::DragFloat("Zoom", &c_zoom, 0.05f, 0.1f, 3.0f); + ImGui::SeparatorText("Settings"); + const char* modes[] = { "Basic" }; + if (ImGui::BeginCombo("Mode", modes[c_mode])) { + for (int i = 0; i < IM_ARRAYSIZE(modes); ++i) { + if (ImGui::Selectable(modes[c_mode], i == c_mode)) { + c_mode = i; + } + } + ImGui::EndCombo(); + } + switch (c_mode) { + case 0: { + ImGui::DragFloat("Sigma", &c_sigma, 0.05); + } break; + } + ImGui::End(); + } + + GL(glViewport(0, 0, wnd_x, wnd_y)); + GL(glEnable(GL_CULL_FACE)); + GL(glCullFace(GL_FRONT)); + GL(glEnable(GL_DEPTH_TEST)); + GL(glEnable(GL_BLEND)); + GL(glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)); + GL(glClearColor(0.1f, 0.1f, 0.1f, 1.0f)); + GL(glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)); + + const float t = SDL_GetTicks() / 1e3f; + const float camt = t * 0.33f; + + Vec3 eye = Vec3(0.0f, 1.5f, 0.0f); + Vec3 tgt = Vec3(0.5f, 0.5f, 0.5f); + eye.x = tgt.x + SDL_sinf(camt) * c_zoom; + eye.z = tgt.z + SDL_cosf(camt) * c_zoom; + Vec3 up = Vec3(0.0f, 1.0f, 0.0f); + + Mat4x4 look = Mat4x4::LookAt(eye, tgt, up); + Mat4x4 proj = Mat4x4::Perspective(70.0f, (float)wnd_x / (float)wnd_y, 0.1f, 10.0f); + Mat4x4 view = proj * look; + + GL(glUniformMatrix4fv(u_view, 1, GL_FALSE, view.Base())) + GL(glUniform3fv(u_cam, 1, eye.Base())); + GL(glUniform1f(u_time, t)); + GL(glUniform1i(u_mode, c_mode)); + GL(glUniform1f(u_sigma, c_sigma)); + + GL(glDrawElements(GL_TRIANGLES, 3 * 12, GL_UNSIGNED_SHORT, NULL)); + + ImGui::Render(); + ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData()); + + if (!SDL_GL_SwapWindow(wnd)) { + fprintf(stderr, "Failed to present window: %s", SDL_GetError()); + return EXIT_FAILURE; + } + } + + SDL_DestroyWindow(wnd); + + return EXIT_SUCCESS; +} -- cgit v1.2.3